Biosynthesis of the Fungal Estrogen F-2 and a Naturally Occuring Derivative (F-3) by Fusarium moniliforme

The fungal metabolites, F-2 and F-3, associated with estrogenism in swine, are produced by some races of Fusarium moniliforme isolated from toxic feeds.     

Effects of angiotensin blockade on the splanchnic circulation in normotensive humans

The effects of angiotensin-converting enzyme inhibition (ACE-I) by enalapril on splanchnic (n = 10) and central hemodynamics (n = 9) were examined in moderately salt-depleted healthy volunteers, at rest and during 15-20 min of lower body negative pressure (LBNP), reducing mean arterial pressure by 10 mmHg. During LBNP before ACE-I, both splanchnic and total peripheral vascular resistances increased. During ACE-I, splanchnic and total peripheral vascular resistances decreased. After enalapril administration, splanchnic vascular resistance did not increase during LBNP. Total peripheral vascular resistance still increased but not to the same extent as during LBNP before ACE-I. The increases in heart rate and plasma norepinephrine during LBNP were attenuated after ACE-I compared with LBNP before ACE-I. The effectiveness of the ACE-I was clearly demonstrated by unchanged and low plasma angiotensin II levels during ACE-I. We conclude that, in normal sodium-depleted humans, acute ACE-I decreases splanchnic vascular resistance at rest and abolishes splanchnic vasoconstriction during LBNP. Furthermore, it may interfere with autonomic nervous system control of the circulation.     

Site-specific aflatoxin B1 adduction of sequence-positioned nucleosome core particles

The question of how the presence of nucleosomal packing of DNA modifies carcinogen interaction at specific sites cannot be answered by studies on whole chromatin or bulk nucleosomes because of the heterogeneity of DNA sequences in the particles. We have circumvented this problem by using nucleosomes that are homogenous in DNA sequence and hence in DNA-histone contact points. A cloned DNA fragment containing a sea urchin 5 S gene which precisely positions a histone octamer was employed. By using 32P end-labeled DNA and genotoxins that allow cleavage at sites of attack, the frequency of adduction at every susceptible nucleotide can be determined on sequencing gels. The small methylating agent dimethyl sulfate and the bulky alkylating agent aflatoxin B1-dichloride (AFB1-Cl2) were used to probe the influence of DNA-histone interactions on DNA alkylation patterns in the sequence-positioned core particle. We find dimethyl sulfate to bind with equal preference to naked or nucleosomal DNA. In contrast, AFB1-Cl2 binding is suppressed an average of 2.4-fold at guanyl sites within nucleosomes compared with AFB1-Cl2 affinity at the corresponding site in naked DNA. The DNA is more accessible in regions near the particle boundary. We observe no other histone-imposed localized changes in AFB1-Cl2 sequence specificity. Further, sites of DNase I cleavage or proposed DNA bending show neither enhanced nor reduced AFB1-Cl2 adduction to N7-guanine. Since AFB1-Cl2 binding sites lie in the major groove, nucleosomal DNA appears accessible to AFB1-Cl2 at all points of analysis but with an access which is uniformly restricted in the central 100 nucleotides of the core particle. The data available do not indicate further localized or site-specific perturbations in DNA interactions with the two carcinogens studied.     

Actinocamax primus arkhangelsky (belemnitellidae; upper cretaceous) biometry,comparison and biostratigraphy

A sample ofActinocamax primus Arkhangelsky, 1912 from the Lower Middle Cenomanian limestones of the Wunstorf quarry west of Hannover (NW Germany) is studied by univariate and bivariate biometric methods in order to analyse the variation of critical characters.A. primus is closely related toA. plenus (Blainville, 1825) but differs from that species by being smaller and more slender.A. primus appears in the Lower Cenomanian and continues into the Lower Middle Cenomanian. It is mainly distributed in the northern part of the North European Palaeobiogeographic Province.A. plenus is recorded from the Middle Cenomanian-lower Lower Turonian of the Russian Platform, but only from the Middle Upper Cenomanian in NW Europe. It is widespread in the North European Province.The primus event in the Lower Middle Cenomanian and theplenus event in the Middle Upper Cenomanian are briefly discussed.     

Consequences of herbivory in the mountain birch (Betula pubescens ssp tortuosa): importance of the functional organization of the tree

Summary Three types of experiments indicate that the functional organization of the mountain birch may influence the ways in which the tree responds to simulated or natural herbivory. The first experiment showed that herbivory to both short and long shoot leaves affects plant development but, because growth largely proceeds by resources of the previous year, is manifested only in the year following the damage. The second experiment showed that even partial damage to a single long shoot leaf caused the axillary bud of that leaf to produce a shorter shoot the next year. Therefore, the value of a leaf depends also on the organ which it is subtending. In the third experiment we manipulated the apical dominance of shoots in ramets and caused improvement to leaf quality in extant shoots. Ramets within a tree responded individually, probably mediated by disturbance of the hormonal control because removal of apical buds elicited the response although removal of the same number of basal buds did not. Induced amelioration is a different response to induced resistance. The two responses are triggered by different cues and may occur in the same plant. By altering hormonal balance of shoots it is potentially possible for herbivores to induce amelioration of food quality. The ways in which herbivory is simulated may explain variability of results obtained when herbivory-induced responses in plants have been studied.     

Experimental avian PMV-2 infection in a domesticated wild host: daily behavior and effect on activity levels

Paramyxovirus type 2 (PMV-2) isolated from wild birds is often considered non-pathogenic, but nothing is known about its effects on overall behavior and fitness of free-flying birds. Domestically bred, African cut-throat finches (Amadina fasciata), a species from which PMV-2 has been isolated in the wild, were inoculated with a Central American field strain of PMV-2. Patterns of behavior were examined before and after viral challenge to quantify inapparent, sublethal effects of the disease. Infected birds demonstrated a significant decrease in activity (P = 0.01) followed by an apparent recovery period. Antibody titers confirmed infection in inoculated birds and indicated that sentinel birds did not become infected.     

Denitrification and oxygen respiration in biofilms studied with a microsensor for nitrous oxide and oxygen

Depth distributions of O₂ respiration and denitrification activity were studied in 1- to 2-mm thick biofilms from nutrient-rich Danish streams. Acetylene was added to block the reduction of N₂O, and micro-profiles of O₂ and N₂O in the biofilm were measured simultaneously with a polarographic microsensor. The specific activities of the two respiratory processes were calculated from the microprofiles using a one-dimensional diffusion-reaction model. Denitrification only occurred in layers where O₂ was absent or present at low concentrations (of a fewM). Introduction of O₂ into deeper layers inhibited denitrification, but the process started immediately after anoxic conditions were reestablished. Denitrification activity was present at greater depth in the biofilm when the NO₃ ^– concentration in the overlying water was elevated, and the deepest occurrence of denitrification was apparently determined by the depth penetration of NO₃ ^–. The denitrification rate within each specific layer was not affected by an increase in NO₃ ^– concentration, and the half-saturation concentration (K_m) for NO₃ ^– therefore considered to be low (<25M). Addition of 0.2% yeast extract stimulated denitrification only in the uppermost 0.2 mm of the denitrification zone indicating a very efficient utilization of the dissolved organic matter within the upper layers of the biofilm.